Female sexual arousal response to implied sexual violence

Background:
There are major physiological and psychological differences between the sexual arousal experiences of men and women. While men generally experience genital and mental arousal simultaneously, these responses seem to act independently from each other in women. It has also been suggested that female genitalia respond to all sexual stimuli, no matter how uninteresting or even aversive the woman finds them. The prevailing theory suggests that this reflexive arousal is a defensive mechanism evolved to protect the genitals during sexual activity with lubrication. This is quite significant in cases of sexual violence. A lack of physical evidence on the survivor's genitalia - or testimony by the rapist that their victim responded, sometimes even to orgasm - can make prosecution of rapists difficult. Additionally, female rape survivors may find their body's response distressing, or think that they somehow "wanted it".
Methods:
We examined female genital response to implied sexual violence. We recruited sexually active University of Texas students with no history of sexual abuse or current sexual dysfunction and measured their mental and physical arousal during two sets of visual erotic stimuli. In the control condition, women were shown displaying positive affect during sexual activity (smiling, actively participating in sex); conversely, the experimental condition featured women showing negative affect (frowning, struggling). Each participant indicated their mental feelings of arousal continuously throughout the stimuli, and vaginal blood flow was recorded as an indicator of physical arousal.
Because patterns of vaginal arousal vary greatly between individuals, each participant's control session was used as a baseline to compare with that participant's experimental session. Analyses included comparing control and experimental sessions on the amount of time taken to reach maximum arousal and the magnitude of maximum arousal, the amount of time spent at relatively high levels of arousal, and the average magnitude of arousal throughout the erotic stimuli.
Results:
We found that participants spent significantly more time aroused while viewing the control (positive affect) stimuli than they did while viewing the experimental (negative affect) stimuli. This was the only significant difference in arousal response between the two conditions.
Conclusions:
Our data may support the theory that genital arousal behaves like a reflex, occurring quickly and strongly immediately after exposure to a sexual stimulus and, if the stimulus is not a preferred sexual cue, dropping off quickly.